The present invention relates to lens mounting structures employed in cameras using detachable lenses, and more specifically, to a combination of camera bodies and lenses having mounting structures for allowing the interchange of lenses between cameras of different formats.
Detachable lens cameras are available in several formats. "Format", in this case, denotes exposable frame size and shape, which is related to the size and shape of the film used in the camera. The exposable frame size determines the minimum imaging circle encompassed by a lens designed for the specific format. The size of the imaging circle by a lens is commonly known as covering power. Cameras of a larger exposable frame size use lenses having greater covering power, while cameras of a smaller exposable frame size use lenses-having lesser covering power.
Conventionally, detachable lenses are not readily interchangeable between cameras of differing formats. More specifically, a detachable lens camera cannot use a lens designed for a smaller format than that of the camera because the covering power is insufficient, and the imaging circle does not fill the exposed frame area, resulting in vignetting of the image.
However, a lens designed for a larger format will have sufficient covering power, and therefore may be optically suitable, but a conventional mounting structure is not able to mount a different or larger format lens. In some cases, adapters are available, but adapters are, by nature, bulky and mechanically complicated, and change the optical properties of the imaging system.